Cardiac alpha-crystallin. II. Intracellular localization.
A major component of the soluble fraction of rat heart is a homopolymer (Mr about 400-650 k) of a small protein (Mr about 20 k). This cardiac protein, which is highly homologous to alpha-B-crystallin, was isolated in its native state and visualized by electron microscopy. A homogeneous population of globular particles with an average diameter of about 14-16 nM could be seen using either negative staining or rotary shadowing procedures. The structures were globular in nature with a central depression (torus-like structures). Polyclonal antibodies, raised against the cardiac crystallin, were used for the immunocytochemical localization of the macromolecular complexes. Using fluorescent secondary antibodies, a clear and sharp striation of fixed and permeabilized rat heart myocytes could be observed, similar to that observed with anti-desmin antibodies and characteristic for the central region of the I-band. Cardiac crystallin was not found associated with F-actin in preparations of rat heart myofibrils. On the other hand, it was a major contaminant of cardiac desmin preparations. These observations suggest that cardiac crystallin is involved in the organization of cytoskeletal filaments of the Z-lines.
Longoni
S
S
Department Pharmaceutical Research, Ciba-Geigy, Basel, Switzerland.
Lattonen
S
S
Bullock
G
G
Chiesi
M
M
D000818:Animals; D003459:Crystallins / Q000032:analysis*; D003600:Cytosol / Q000737:chemistry / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D009206:Myocardium / Q000737:chemistry* / Q000648:ultrastructure; D011487:Protein Conformation; D051381:Rats
D003459:Crystallins